I understand that if that equation is negative then the acceleration of the scale constant is concave down. But then doesn't that mean that we must know the sign of a double dot and a dot? For example it tells us that a(t) is concave down. but what if it were a function like this...
Friedmann's Eq can be viewed here https://ned.ipac.caltech.edu/level5/March08/Frieman/Equations/paper1x.gif
What I don't get is that all the texts/analyses of Friedmann's equation say that if the right hand side is negative it means that the universe will expand reach a critical point and then...